Currently, high-speed communications rely on fiber optics for high data transmission rates and high bandwidth capacities. Through fiber optics, light emitting diodes (LEDs) and lasers are adapted to produce digital data in the form of light signals. These light signals are propagated through a fiber optic cable and, at some point, are converted back to electrical signals for processing. Optical subassemblies are used for this data conversion.
One type of optical subassembly is referred to as a transmitter optical subassembly or “TOSA”. The TOSA includes an electrical interface for receiving electrical signals, a data encoder/modulator adapted to convert the electrical signals into suitable optical signals, and a light emitting diode or laser to produce light pulses that form a light signal. Thereafter, the light signal passes through a lens for transmission over an optical fiber.
Similarly, a receiver optical subassembly (ROSA) is used to translate light signals into electrical signals. Conventionally, a ROSA comprises an optical fiber receptacle and a photodiode. Typically, the light exiting an optical fiber in the optical fiber receptacle is so divergent that it needs to be collimated or otherwise focused onto the photodiode by a lens.
In an effort to reduce the costs of fiber optic modules, optical subassemblies, most commonly ROSAs, have been implemented with plastic housings. While a plastic ROSA housing is cost effective and less sensitive to electrostatic discharge, it experiences increased electromagnetic interference (EMI) leakage. More specifically, electromagnetic (EM) waves inside the module can permeate through plastic and escape through openings within the fiber optic module, thereby causing the failure in passing Federal Communications Commission (FCC) EMI requirements.